ETDs

This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.

In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.

Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.

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Radiation Effects on In-Memory Computing Architectures

Description
Recently, the implementation of neuromorphic accelerator hardware has gradually changed from traditional Von Neumann architectures to non-Von Neumann architectures due to the “memory wall” and “power wall”. Near-memory computing (NMC) and In- memory computing (IMC) are two common types of non-Von Neumann approaches. NMC can help reduce data movements, yet…

Recently, the implementation of neuromorphic accelerator hardware has gradually changed from traditional Von Neumann architectures to non-Von Neumann architectures due to the “memory wall” and “power wall”. Near-memory computing (NMC) and In- memory computing (IMC) are two common types of non-Von Neumann approaches. NMC can help reduce data movements, yet it cannot fully address the challenge of improving computational efficiency as the neural network size grows. IMC has been proposed as a superior alternative. This architecture performs computation inside the memory array using stackable synaptic devices to improve the latency and the energy efficiency of neural network accelerators. Both volatile and non-volatile computational memory devices can achieve IMC. Fully complementary metal-oxide semiconductor (CMOS) in-memory computing cells can be realized by adding additional transistors in standard static random access memory (SRAM) bit-cell. The SRAM-based designs investigated in this dissertation perform bit-wise logical operation to obtain XNOR-and-accumulate computation (XAC) for deep neural networks (DNNs). Hybrid in-memory computing architectures combine CMOS with embedded non-volatile memory (eNVM). Resistive random access memory (RRAM) is one class of eNVM ideally suited for hybrid IMC. In a neural network, RRAM with programmable multi-level resistance/conductance states can naturally emulate weight transitions in the synaptic elements of neural networks. In this dissertation, the operation and effects of ionizing radiation effects on both fully CMOS and hybrid IMCs are investigated. The fully CMOS architectures preform SRAM-based XAC computations. The hybrid architectures use multi-state RRAM synapse with CMOS neurons to perform multiply-and-accumulate computation (MAC). In the SRAM XAC array, an 8×8 XNOR IMC array is modeled with flipped-well enhanced-gate super low threshold voltage (EGSLVT) metal-oxide semiconductor field-effect transistors (MOSFETs) from the GlobalFoundries 22nm fully depleted silicon on insulator (FDSOI) process. The impact of total ionizing dose (TID) on the XAC synaptic array is analyzed by using radiation-aware models to mimic TID-induced voltage shifts in MOSFETs. In multi- state RRAM MAC array, 4-state conductance has been programmed in hafnium-oxide (HfOx) RRAM 1-transistor-1-resistor (1T1R) array. The impact of total ionizing dose on the multi-state behavior of HfOx RRAM is evaluated by irradiating a 64kb 1T1R array with 90nm CMOS peripheral circuitry under Co-60 γ-ray irradiation.
ContributorsHan, Xu (Author) / Barnaby, Hugh (Thesis advisor) / Kozicki, Michael (Committee member) / Marinella, Matthew (Committee member) / Esqueda, Ivan (Committee member) / Arizona State University (Publisher)
Created2022
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Conductive Bridge Random Access Memory (CBRAM) as an Analog Synapse for Neuromorphic Computing

Description
The Deep Neural Network (DNN) is one type of a neuromorphic computing approach that has gained substantial interest today. To achieve continuous improvement in accuracy, the depth, and the size of the deep neural network needs to significantly increase. As the scale of the neural network increases, it poses a…

The Deep Neural Network (DNN) is one type of a neuromorphic computing approach that has gained substantial interest today. To achieve continuous improvement in accuracy, the depth, and the size of the deep neural network needs to significantly increase. As the scale of the neural network increases, it poses a severe challenge to its hardware implementation with conventional Computer Processing Unit (CPU) and Graphic Processing Unit (GPU) from the perspective of power, computation, and memory. To address this challenge, domain specific specialized digital neural network accelerators based on Field Programmable Gate Array (FPGAs) and Application Specific Integrated Circuits (ASICs) have been developed. However, limitations still exist in terms of on-chip memory capacity, and off-chip memory access. As an alternative, Resistive Random Access Memories (RRAMs), have been proposed to store weights on chip with higher density and enabling fast analog computation with low power consumption. Conductive Bridge Random Access Memories (CBRAMs) is a subset of RRAMs, whose conductance states is defined by the existence and modulation of a conductive metal filament. Ag-Chalcogenide based Conductive Bridge RAM (CBRAM) devices have demonstrated multiple resistive states making them potential candidates for use as analog synapses in neuromorphic hardware. In this work the use of Ag-Ge30Se70 device as an analog synaptic device has been explored. Ag-Ge30Se70 CBRAM crossbar array was fabricated. The fabricated crossbar devices were subjected to different pulsing schemes and conductance linearity response was analyzed. An improved linear response of the devices from a non-linearity factor of 6.65 to 1 for potentiation and -2.25 to -0.95 for depression with non-identical pulse application is observed. The effect of improved linearity was quantified by simulating the devices in an artificial neural network. Simulations for area, latency, and power consumption of the CBRAM device in a neural accelerator was conducted. Further, the changes caused by Total Ionizing Dose (TID) in the conductance of the analog response of Ag-Ge30Se70 Conductive Bridge Random Access Memory (CBRAM)-based synapses are studied. The effect of irradiation was further analyzed by simulating the devices in an artificial neural network. Material characterization was performed to understand the change in conductance observed due to TID.
ContributorsApsangi, Priyanka (Author) / Barnaby, Hugh (Thesis advisor) / Kozicki, Michael (Committee member) / Sanchez Esqueda, Ivan (Committee member) / Marinella, Matthew (Committee member) / Arizona State University (Publisher)
Created2022